This invention relates generally to an article of footwear having an outer sole, a lateral sole margin, and an inner sole, and to a process and apparatus for its manufacture.
Such an article of footwear is disclosed in East German Patent No. 64882 in which an outer sole and a lateral sole integrally formed therewith, and of polyvinylchloride, are produced as a unit at a first work station. The inner sole, which may consist of a mixture of isocyanate and a polyol which reacts into polyurethane, is produced at a second work station at which the inner sole is molded simultaneously onto the outer sole, the lateral sole and the bottom of the shoe upper.
At one work station the outer sole and the lateral sole can be formed from molded rubber material which vulcanizes to form a unitary outer sole and lateral sole. The inner sole is then formed of molded rubber material and bonded with the outer sole, the lateral sole and the shoe last. Contact between the vulcanized rubber material of the outer sole and lateral sole with the inner sole is made mechanically in that the mixture that reacts into polyurethane, when considered microscopically, to a certain extent grabs, as if with claws, in the common contact zone which contains fissures. This mechanical bond is adequate in many, circumstances, but may be inadequate, for example, for use as mountain climbing boots, sports shoes for jogging, and the like.
Moreover, since the outer sole and the lateral sole, formed together as a unit, are of the same rubber material, it is not possible to select a different rubber material, for example, a highly abrasion resistant rubber material for the outer sole, and to select a rubber material for the lateral sole which is less abrasion-resistant but nevertheless elastic, so as to provide the necessary cushioning qualities which to a large extent relieves the spinal column of the wearer of concussion-like effects.
Circular turntable installations providing a plurality of molding stations are generally disclosed in Publication No. DESMA 521S-526S, Klickner-Ferromatik Desma GmbH, and entitled "Injection Molding Machine For Direct Attachment Of Soles." The circular turntable installations have two devices for the mixing of isocyanate and a polyol into a mixture reacting into polyurethane which, depending on the mixing ratio and the additives, reacts into a wear-resistant outer sole or a flexible inner sole.
The circular turntable is rotated incrementally for molding the outer soles and the inner soles. The molding stations are stopped during incremental movement and interlocked when stopped relative to the two mixing and injection devices.
These devices are located along the periphery of the turntable and are movable in a radial direction toward the turntable. The molding apparatus at each station has two lateral molding elements which, in a mold closed position, define an opening and two sprue channels.
A vertically movable last turning body is mounted on the apparatus above the lateral mold elements, the body having a counterstamp and a shoe last for supporting the shoe uppers.
A vertically adjustable bottom stamp is located below the lateral mold elements. The bottom stamp, lateral mold elements in their mold closing position and the counterstamp together define a mold cavity into which the mixture reacting into the outer sole is introduced. The bottom stamp which contains the molded outer sole, the lateral mold elements in a mold closed position, and the shoe last which supports the shoe upper together define a mold cavity for molding the inner sole as the mixture reacting into the inner sole is introduced into the mold cavity which, in the course of the reaction, bonds to the outer sole and to the shoe upper.
U.S. Ser. No. 942,832, among the aforementioned related applications, discloses molding stations on a circular turntable for the molding of shoe soles with an outer sole of elastomer and an inner sole of polyurethane.
For the molding of the outer sole of elastomer, there is provided, in lieu of a previously employed device for mixing the mixture reacting into polyurethane, a plastification and injection aggregate device for plastification of the elastomer, as employed in injection molding machines for the processing of thermoplastic synthetic materials, and for injection of the elastomer into the outer sole mold cavity. Since high pressures occur during the injection of the plastified elastomer, the molding apparatus at each station is provided with an upper, vertically adjustable cross block supporting a pivotably mounted mold carrier with pairs of opposing heatable mold parts lying parallel to the pivot axis, each mold part defining a mold cavity for the outer sole and including cooling channels.
A lower, vertically adjustable cross block below the first cross block has a heatable plate facing the mold carrier and cooperates with the heatable mold parts thereof for the production of outer soles. Above the upper vertically moveable cross block is a fixed cross block having an opening into which a heatable mold part with a molded outer sole in its mold cavity projects and combines together with laterally movable mold elements, located above the fixed cross block, for the molding of an inner sole of polyurethane.
The mixtures which react into polyurethane for the outer sole and/or for the inner sole essentially consist of a polyol and isocyanate, as well as chain extenders and catalysts, which are adjusted by the respective additives for the desired material properties of the outer soles and/or inner soles, whereby the outer sole is rendered wear resistant and the inner sole flexible having a porous structure.
The chemical reaction starts with the mixing of the components. In the mold, the mixtures react into outer soles or inner soles. During the reaction into the inner sole, the molding of the sole takes place simultaneously with the bonding to the shoe upper and to the outer sole.
The outer sole of elastomer and the inner sole of polyurethane are bonded in the area of their contacting surfaces by chemical bonds between isocyanate and reactive end groups of the substances added to the elastomer.
As likewise employed for the present invention, the mixtures reacting into polyurethane are mixtures on the basis of ether or esterpolyols, containing on the basis of 100 parts by weight:
30-100 parts by weight isocyanate; PA1 0.1-10 parts by weight catalyst; PA1 the remainder chain expanders; and PA1 other usual additives. PA1 phenolformaldehyde resins, e.g. PA1 methylolized phenolformaledhyde resins, e.g.: PA1 resorcin in connection with a formaldehyde dispenser, e.g.: PA1 silicic acid fillers, e.g.: PA1 aminoalcohol, e.g.: PA1 primary or secondary amine, e.g.: PA1 polyvinylalcohol, e.g.: PA1 high hydroxylgroup containing polyol, e.g.: PA1 Acrylate rubber (ACM) e.g.: PA1 or a combination of the above substances.
The catalyst which may be used is DABCO-SB produced by Airproducts Company.
The outer soles are made from elastomers which can be mixed with the following chemical compounds or chemical substances in quantitative shares of 0-20 phr, relative to the rubber amount: e.g., acryl-nitryl-rubber, styrol-butadiene-rubber, natural rubber, chloroprene-rubber.
The outer soles can generally be produced from any known rubber quantities if, for example, the following substances are mixed in quantities of 0-20 phr (quantity relative to the amount of rubber used):
Vulkadur A (Bayer AG) PA2 Coretack (BASF) PA2 SP 1045 (Krahn) PA2 Korever (BASF) PA2 Cohedur A (Bayer AG) PA2 Cohedur RS (Bayer AG) PA2 Cohedur RK (Bayer AG) PA2 Vulkasil S (Bayer AG PA2 Ultrasil (Degussa) PA2 3-amino-propanol PA2 Stearylamine PA2 Mowiwol (Hoechst) PA2 VSH 72 (AIR PRODUCTS) PA2 VSH 73 (AIR PRODUCTS) PA2 Formrez (Witco) PA2 Hydrin (Polysar) PA2 Hercolor (Hercules)
The formation of the outer sole of the elastomer is carried out in such a manner that the elastomers plastify at the usual processing temperatures and are injected into the mold cavities according to the usual technology and corresponding high pressures of injection molding machines.
The control of the temperature of the elastomers is carried out such that the temperature of the injected outer soles is cooled to just below the decomposition temperature of the polyurethane for the inner sole to be produced and then the mixture reacting into the polyurethane is brought into contact with the outer sole, whereby in the contacting surfaces between the elastomer and the reacting polyurethane isocyanate reacts with the reactive end groups.